Resettable drive mechanism for a medication delivery device and medication delivery device

ABSTRACT

A resettable drive mechanism for a medication delivery device is proposed, said mechanism comprising a housing ( 13, 17, 40 ) with a proximal end and a distal end, a drive member ( 20 ) rotatable with respect to the housing in a second direction for delivering a dose of a medication, a piston rod adapted to be driven in a distal direction with respect to the housing by the drive member, when the drive member rotates in the second direction, a stop member adapted to prevent rotation of the drive member in a first direction opposite to the second direction with respect to the housing, when the stop member engages the drive member, and a clutch member movable with respect to the housing between a delivery position and a reset position, wherein, when the clutch member is in the delivery position, the stop member and the drive member are engaged and the drive member is prevented from rotating in the first direction with respect to the housing, and when the clutch member is in the reset position, the drive member and the stop member are disengaged, the drive member is rotatable in the first direction with respect to the housing and the piston rod is movable in the proximal direction with respect to the housing. Furthermore, a medication delivery device is provided.

The present invention relates to a resettable drive mechanism for amedication delivery device and a medication delivery device comprisingsuch a drive mechanism.

In a medication delivery device, a piston within a cartridge thatcontains medication may be displaced with respect to the cartridge inthe distal direction by a piston rod which moves in the distal directionwith respect to the cartridge. Thereby, a dose of medication can beexpelled from the cartridge. A medication delivery device is describedin US 2007/0123829 A1, for example.

In order to provide for a reusable device, after the cartridgecontaining the medication has been emptied, the piston rod often has tobe moved back from a distal end position to a proximal startingposition.

It is an object to provide for an improved resettable drive mechanism.Also, an improved medication delivery device should be provided for.

This object may be achieved by a drive mechanism according to theindependent claim. Further features, advantages and expediencies aresubject matter of the dependent claims.

A resettable drive mechanism for a medication delivery device comprisesa housing with a proximal end and a distal end, a drive member rotatablewith respect to the housing in a second direction for delivering a doseof a medication, a piston rod adapted to be driven in a distal directionwith respect to the housing by the drive member, when the drive memberrotates in the second direction, a stop member adapted to preventrotation of the drive member in a first direction opposite to the seconddirection with respect to the housing, when the stop member engages thedrive member, and a clutch member movable with respect to the housingbetween a delivery position and a reset position.

When the clutch member is in the delivery position, the stop member andthe drive member are engaged, and the drive member is prevented fromrotating in the first direction with respect to the housing. When theclutch member is in the reset position, the drive member and the stopmember are disengaged, the drive member is rotatable in the firstdirection with respect to the housing and the piston rod is movable inthe proximal direction with respect to the housing.

Preferably, the clutch member is (linearly) displaced with respect tothe housing when the clutch member is moved from the delivery positioninto the reset position or from the reset position into the deliveryposition. The clutch member may be displaced with respect to one of thedrive member and the stop member when the clutch member is moved fromthe delivery position into the reset position or from the reset positioninto the delivery position. The other one of the drive member and thestop member may follow movement of the clutch member when the clutchmember is moved from the delivery position into the reset position orfrom the reset position into the delivery position. Via this relativemovement, drive member and stop member may be disengaged.

By providing for the clutch member which is movable with respect to thehousing between a delivery position and the reset position, moving thepiston rod in the proximal direction with respect to the housing isfacilitated. In particular, since the drive member may be rotated in thefirst direction with respect to the housing, the drive member may rotatein that direction which is opposite to the one during delivery of thedose of medication without the rotational movement in the firstdirection being prevented by the stop member. Thus, proximal movement ofthe piston rod which may cause the drive member to be rotated in thefirst direction is no longer prevented and resetting of the drivemechanism is facilitated.

Stop member and drive member may be permanently engaged while the clutchmember is in delivery position. The drive member may engage the pistonrod. The drive member may be permanently engaged with the piston rodregardless whether the clutch member is in delivery position or in thereset position.

Rotational movement of the drive member may be converted into rotationalmovement of the piston rod in the same direction. Rotational movement ofthe piston rod may be converted into displacement of the piston rod withrespect to the housing in the distal direction, for example by athreaded engagement of the piston rod with the housing. The piston rodmay be displaced in the distal direction with respect to the housing androtate in the second direction during the distal displacement. Thepiston rod may be displaced along its rotation axis.

Alternatively, rotational movement of the drive member may be convertedinto pure (linear) displacement of the piston rod with respect to thehousing. Thus, the piston rod may move translationally with respect tothe housing without rotating. A displacement axis of the piston rod mayrun transversely with respect to the rotation axis around which thedrive member rotates.

In a preferred embodiment, the drive mechanism comprises a clutchresilient member, preferably a clutch spring member. The clutchresilient member may be biased when the clutch member is in the deliveryposition. The clutch resilient member may be fully or partly relaxedwhen the clutch member is in the reset position. The clutch resilientmember may be arranged to exert a force on the clutch member which forcetends to move the clutch member in the reset position when the clutchmember is moved towards the delivery position or is in the deliveryposition.

In another preferred embodiment, the drive mechanism comprises a clutchstop member. The clutch stop member may be movable with respect to theclutch member. The clutch stop member may be removable, in particularfrom the drive mechanism. The clutch stop member may be arranged tokeep, preferably to hold, the clutch member in the delivery position.The clutch stop member may be provided for preventing movement of theclutch member towards the reset position. The clutch stop member may bearranged to counteract the force exerted by the clutch resilient memberthat tends to move the clutch member in the reset position. The clutchstop member is preferably releasably secured with respect to thehousing. If the clutch stop member is removed from the clutch member,e.g. detached from the housing, the clutch member is permitted to moveinto the reset position after the clutch stop member has been removed.

Thus, the clutch stop member may keep the drive mechanism in a deliverystate by preventing movement of the clutch member towards the resetposition. If the clutch stop member is removed from the clutch member,the clutch member may be moved into the reset position, which movementputs the drive mechanism in a reset state.

The clutch stop member and the clutch resilient member, in combination,facilitate provision of an automatically actuated reset mechanism for adrive mechanism. Due to the biased clutch resilient member the clutchmember is moved automatically into reset position when the clutch stopmember is removed.

In another preferred embodiment, the drive mechanism comprises aresilient member, preferably a spring member. The resilient member maybe arranged to keep the stop member and the drive member in abutmentand/or engagement. The resilient member may exert a force on one of orboth of the drive member and the stop member which force tends to keepthe drive member and the stop member in engagement. Preferably, thisforce has to be overcome for disengaging drive member and stop member.

In another preferred embodiment, the clutch resilient member is a clutchspring member and the resilient member is a spring member. The clutchspring member preferably has a spring strength which is greater than aspring strength of the spring member. Thus, the clutch resilient membermay exert a force on the clutch member which overcomes the force exertedby the resilient member by which the stop member and the drive memberare kept in abutment and/or engagement. Accordingly, disengaging stopmember and drive member is facilitated.

In another preferred embodiment, the stop member and the drive memberare arranged to be moved into engagement when the clutch member is movedfrom the reset position towards the delivery position. The force exertedby the resilient member may assist this movement. An additional externalforce may be applied for (re-)engaging stop member and drive member. Itmay be necessary to overcome the force exerted by the clutch resilientmember for (re-)engaging stop member and drive member.

In another preferred embodiment, the drive member and the stop memberare engaged to form a unidirectional friction clutch mechanism when theclutch member is in the delivery position. Accordingly, relativerotational movement of the drive member with respect to the stop memberand, in particular, with respect to the housing in the first directionis prevented when the clutch member is in the delivery position.

In another preferred embodiment, the stop member is secured againstrotational movement with respect to the housing and the stop member isdisplaceable with respect to the housing.

In another preferred embodiment, the stop member is arranged to followmovement of the clutch member towards the reset position, therebydisengaging from the drive member.

In another preferred embodiment, the clutch member is arranged to abutthe stop member when the clutch member is moved towards the resetposition. Preferably, the clutch member carries the stop member with ittowards the reset position after having moved into abutment with thestop member.

Another aspect relates to a medication delivery device comprising aresettable drive mechanism as described above. The medication deliverydevice additionally comprises a cartridge for holding a medication, thecartridge being releasably attached to the housing.

Features which are described herein above and below in connection withthe drive mechanism may also be applied for the corresponding medicationdelivery device and vice versa.

In a preferred embodiment of the medication delivery device, thecartridge or a cartridge retaining member, which is adapted to retainand/or attach the cartridge to the housing, is the clutch stop member.Thus, the cartridge or the cartridge retaining member may prevent theclutch member from moving into the reset position on account of theforce exerted by the clutch resilient member. If the cartridge retainingmember or the cartridge is detached from the housing, the clutch memberwill automatically move into reset position.

Further features, embodiments and expediencies for the drive mechanismor the medication delivery device become apparent from the followingdescription of exemplary embodiments in conjunction with the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a partly sectional side view of an exemplaryembodiment of a medication delivery device.

FIG. 2 schematically shows a perspective sectional view of a part of adrive mechanism according to a first embodiment with schematicallyindicated movements of elements thereof during setting of a dose.

FIG. 3 schematically shows a more detailed side view of a part of FIG.2.

FIG. 4 schematically shows a perspective sectional view of a part of thedrive mechanism according to the first embodiment with indicatedmovements of elements thereof during delivery of a dose.

FIG. 5 schematically shows a more detailed side view of a part of FIG.4.

FIG. 6 schematically shows a perspective sectional view of a part of adrive mechanism that is configured in accordance with the firstembodiment.

FIG. 7 schematically shows a perspective view of a part of the drivemechanism of FIG. 2 with indicated movements of elements thereof duringdelivery of a dose.

FIG. 8 schematically shows a perspective view of a part of a drivemechanism that is configured in accordance with the first embodiment.

FIG. 9 schematically shows a perspective view of a part of a drivemechanism that is configured in accordance with the first embodiment.

FIG. 10 schematically shows an oblique sectional view of a drivemechanism according to a second embodiment.

FIG. 11 schematically shows an oblique sectional view of a drivemechanism according to a third embodiment.

FIG. 12 schematically shows an oblique sectional view of a part of thedrive mechanism of FIG. 11.

FIG. 13 schematically shows an oblique sectional view of a part of thedrive mechanism of FIG. 11.

FIG. 14 schematically shows an oblique sectional view of a part of thedrive mechanism of FIG. 11.

FIG. 15 schematically shows an oblique sectional view of a part of thedrive mechanism of FIG. 11.

FIG. 16 shows a schematic sectional view of a part of a resettable drivemechanism according to an embodiment in delivery position.

FIG. 17 shows the resettable drive mechanism of FIG. 16 in resetposition.

Like elements, elements of the same kind and identically acting elementsare provided with the same reference numerals in the figures.

Turning now to FIG. 1, a medication delivery device 1 comprises acartridge unit 2 and a drive unit 3. The cartridge unit 2 comprises acartridge 4. Medication 5 is retained in the cartridge 4. The medication5 is preferably liquid medication. The cartridge 4 preferably comprisesa plurality of doses of the medication 5. The medication 5 may compriseinsulin, heparin, or growth hormones, for example. The cartridge 4 hasan outlet 6 at its distal end. Medication 5 can be dispensed from thecartridge through outlet 6. The device 1 may be a pen-type device, inparticular a pen-type injector. The device 1 may be a disposable or areusable device. The device 1 may be a device configured to dispensefixed doses of the medication or variable, preferably user-settable,doses. The device 1 may be a needle-based or a needle free device. Thedevice 1 may be an injection device.

The term “distal end” of the medication delivery device 1 or a componentthereof may refer to that end of the device or the component which isclosest to the dispensing end of the device 1. The term “proximal end”of the medication delivery device 1 or a component thereof may refer tothat end of the device or the component which is furthest away from thedispensing end of the device. In FIG. 1, the distal end of the device 1was assigned reference numeral 7 and the proximal end of the device wasassigned reference numeral 8.

The outlet 6 may be covered by a membrane 9, which protects medication 5against external influences during storage of the cartridge. Formedication delivery, membrane 9 may be opened, e.g. pierced. Forexample, membrane 9 may be pierced by a needle unit (not explicitlyshown). The needle unit may be (releasably) attached to the distal endof the cartridge unit 2. The needle unit may provide for fluidcommunication from the inside of the cartridge 4 to the outside of thecartridge through outlet 6.

A piston 10 is retained within the cartridge 4. The piston 10 is movablewith respect to the cartridge. The piston 10 may seal the medication 5within the cartridge. The piston 10 expediently seals the interior ofthe cartridge 4 proximally. Movement of the piston 10 with respect tothe cartridge 4 in the distal direction causes medication 5 to bedispensed from the cartridge through outlet 6 during operation of thedevice.

The cartridge unit 2 furthermore comprises a cartridge retaining member11. The cartridge 4 is retained within the cartridge retaining member11. The cartridge retaining member 11 may stabilize the cartridge 4mechanically. Additionally or alternatively, the cartridge retainingmember 11 may be provided with a fixing member (not explicitly shown)for attaching the cartridge unit 2 to the drive unit 3.

The cartridge unit 2 and the drive unit 3 are secured to one another,preferably releasably secured. A cartridge unit 2 which is releasablysecured to the drive unit may be detached from the drive unit 3, forexample in order to allow for providing for a new cartridge 4, if all ofthe doses of medication which once were in the cartridge formerlyattached to the drive unit 3 have already been dispensed. The cartridgeretaining member 11 may be releasably secured to the drive unit 3 via athread, for example.

Alternatively, the cartridge retaining member 11 may be dispensed with.It is particularly expedient, in this case, to apply a robust cartridge4 and to attach the cartridge directly to the drive unit 3.

The drive unit 3 is configured for transferring force, preferablyuser-exerted force, particularly preferably manually exerted force, tothe piston 10 for displacing the piston 10 with respect to the cartridge4 in the distal direction. A dose of medication may be dispensed fromthe cartridge in this way. The size of the delivered dose may bedetermined by the distance by which the piston 10 is displaced withrespect to the cartridge 4 in the distal direction.

The drive unit 3 comprises a drive mechanism. The drive mechanismcomprises a piston rod 12. The piston rod 12 may be configured fortransferring force to the piston 10, thereby displacing the piston inthe distal direction with respect to the cartridge 4. A distal end faceof the piston rod 12 may be arranged to abut a proximal end face of thepiston 10. A bearing member (not explicitly shown) may be arranged toadvance the piston 10, preferably to abut the proximal end face of thepiston 10. The bearing member may be arranged between piston 10 andpiston rod 12. The bearing member may be fixed to the piston rod 12 or aseparate member. If the piston rod 12 is configured to be rotated duringoperation of the device, for example during dose delivery, it isparticularly expedient to provide for a bearing member. The bearingmember may be displaced together with the (rotating) piston rod withrespect to the housing. The piston rod may be rotatable with respect tothe bearing member. In this way, the risk that the rotating piston roddrills into the piston and thereby damages the piston is reduced.Accordingly, while the piston rotates and is displaced with respect tothe housing, the bearing member is preferably only displaced, i.e. doesnot rotate. The piston rod may be bounded by the bearing member.

The drive unit 3 comprises a housing 13 which may be part of the drivemechanism. The piston rod 12 may be retained in the housing. A proximalend side 14 of the cartridge unit 2 may be secured to the drive unit 3at a distal end side 15 of the housing 13, for example via a threadedconnection. Housing 13, cartridge 4 and/or cartridge retaining member 11may have a tubular shape.

The term “housing” shall preferably mean any exterior housing (“mainhousing”, “body”, “shell”) or interior housing (“insert”, “inner body”)which may have a unidirectional axial coupling to prevent proximalmovement of specific components. The housing may be designed to enablethe safe, correct, and comfortable handling of the medication deliverydevice or any of its mechanism. Usually, it is designed to house, fix,protect, guide, and/or engage with any of the inner components of themedication delivery device (e.g., the drive mechanism, cartridge,piston, piston rod), preferably by limiting the exposure tocontaminants, such as liquid, dust, dirt etc. In general, the housingmay be unitary or a multipart component of tubular or non-tubular shape.

The term “piston rod” shall preferably mean a component adapted tooperate through/within the housing, which may be designed to transferaxial movement through/within the medication delivery device, preferablyfrom the drive member to the piston, for example for the purpose ofdischarging/dispensing an injectable product. Said piston rod may beflexible or not. It may be a simple rod, a lead-screw, a rack and pinionsystem, a worm gear system, or the like. “piston rod” shall further meana component having a circular or non-circular cross-section. It may bemade of any suitable material known by a person skilled in the art andmay be of unitary or multipart construction.

The drive unit 3 comprises a dose part 16. The dose part 16 is movablewith respect to the housing 13. The dose part 16 may be movable in theproximal direction with respect to the housing for setting of a dose ofthe medication 5 which is to be delivered and in the distal directionwith respect to the housing for delivery of the set dose. The dose part16 is preferably connected to the housing 13. The dose part 16 may besecured against rotational movement with respect to the housing. Thedose part 16 may be moved (displaced) between a proximal end positionand a distal end position with respect to the housing 13 (not explicitlyshown). The distance by which the dose part is displaced with respect tothe housing during setting of the dose may determine a size of the dose.The proximal end position and the distal end position may be determinedby a respective stop feature which may limit the proximal ordistaltravel of the dose member with respect to the housing. The device 1 maybe a variable dose device, i.e. a device configured for delivering dosesof medication of different, preferably user-settable, sizes.Alternatively, the device may be a fixed dose device.

The device 1 may be a manually, in particular non-electrically, drivendevice. The (user-applied) force which causes the dose part 16 to bemoved with respect to the housing 13 in the distal direction may betransferred to the piston rod 12 by the drive mechanism. For thispurpose, other elements of the drive mechanism may be provided which arenot explicitly shown in FIG. 1. The drive mechanism is preferablyconfigured to not move the piston rod 12 with respect to the housing 13when the dose part is moved in the proximal direction with respect tothe housing for setting of the dose.

Embodiments of a drive mechanism which are suitable to be provided inthe medication delivery device 1 as it was described above are describedin more detail below.

A first embodiment of a drive mechanism which is suitable for beingimplemented in the medication delivery device 1 as described above isdescribed in connection with FIGS. 2 to 9.

The drive mechanism comprises a housing part 17. The housing part 17 hasa proximal end 18 and a distal end 19. The housing part 17 may be(outer) housing 13 of FIG. 1, a part thereof or an insert within housing13, which insert is preferably secured against rotational and axialmovement with respect to housing 13. The housing part 17 may be aninsert sleeve, for example. The insert sleeve may be snap-fitted orglued to housing 13, for example. The housing part 17 may have a tubularshape. Housing part 17 may comprise outer fixing elements 64, forexample snap-fit elements, for fixing housing part 17 to housing 13 (cf.FIG. 8).

The piston rod 12 is retained in the housing 13, preferably withinhousing part 17. The piston rod 12 is driven in the distal directionwith respect to the housing part 17 during dose delivery.

The drive mechanism furthermore comprises a drive member 20. Drivemember 20 is retained within the housing part 17. Drive member 20 isconfigured to transfer force, preferably torque, to the piston rod 12.The transferred force may cause the piston rod 12 to be displaced in thedistal direction with respect to the housing part 17 for dose delivery.

Drive member 20 is rotatable with respect to housing part 17. The drivemember 20 may engage the piston rod 12. Rotational movement of the drivemember, for example rotational movement in a second direction may beconverted into distal movement of the piston rod 12 with respect to thehousing part 17. This is explained in more detail below.

The drive mechanism furthermore comprises a rotation member 21. Therotation member 21 is rotatable with respect to the housing part 17 in afirst direction, in particular for setting of a dose of the medication,and in a second direction, in particular for delivering the set dose.The second direction is opposite to the first direction. The firstdirection may be counter-clockwise and the second direction may beclockwise as seen from the proximal end of the device, for example.

Drive member, rotation member and/or piston rod are preferablyconfigured to be rotatable about a (common) rotation axis. The rotationaxis may extend through drive member, rotation member and/or piston rod.The rotation axis may be the main longitudinal axis of the piston rod.The rotation axis may run between the proximal end and the distal end ofthe housing part 17.

The rotation member 21 is coupled to the drive member 20 by anunidirectional clutch mechanism, in particular a friction clutchmechanism. This clutch mechanism permits rotational movement of therotation member 21 with respect to the drive member 20 when the rotationmember rotates in the first direction with respect to the housing part17. The clutch mechanism prevents rotational movement of the rotationmember 21 with respect to the drive member 20, when the rotation memberrotates in the second direction with respect to the housing part 17. Thedrive member 20 may thus follow rotational movement of the rotationmember 21 in the second direction with respect to the housing part 17.

The drive member 20 is arranged to abut and/or engage the rotationmember and, in particular, engages rotation member 21. The drive member20 comprises a toothing 22 at one end, e.g. its proximal end. Therotation member comprises a toothing 23 at one end which end faces thedrive member 20, e.g. its distal end. Toothing 22 comprises a pluralityof teeth 24. Toothing 23 comprises a plurality of teeth 25. Teeth 24and/or 25 may extend along the rotation axis. Toothings 22 and 23 may beconfigured to mate with one another.

A respective tooth of teeth 24 and/or teeth 25 may be ramp-shaped, inparticular along the azimuthal (angular) direction as seen from therotation axis. The ramp of the respective tooth is limited (in theangular direction) by a steep end face of that tooth, i.e. a face of thetooth that runs parallel to the rotation axis or includes a smallerangle with the rotation axis when projected on this axis than the rampwhen projected on this axis. The steep end face is followed by the rampof the next tooth.

The teeth 24 may be disposed along the perimeter of that end of thedrive member 20 which faces the rotation member 21. The teeth 25 may bedisposed along the perimeter of the rotation member 21 at that end whichfaces the drive member 20.

When the steep end faces of two teeth abut and the rotation member isrotated further on in the second direction, the steep sides stay inabutment and drive member 20 follows the rotation of rotation member 21.When the rotation member rotates in the first direction, the ramp of theteeth—which ramps, in particular, run obliquely with respect to therotation axis—slide along each other and, in consequence, the rotationmember 21 may rotate with respect to the drive member 20.

The drive mechanism furthermore comprises a stop member 26. The drivemember may be arranged between the stop member 26 and the rotationmember 21. The stop member 26 is configured for preventing rotationalmovement of the drive member 20 in the first direction with respect tothe housing part 17 during setting of a dose, i.e. when the rotationmember rotates in the first direction. Thus, the rotation member 21 mayrotate in the first direction with respect to the housing part 17,whereas the drive member 20 and the stop member 21 don't rotate.

The stop member 26 is coupled to the drive member 20 by anotherunidirectional clutch mechanism, in particular a friction clutchmechanism. This clutch mechanism prevents rotational movement of thedrive member 20 with respect to the stop member 20 when the rotationmember rotates in the first direction with respect to the housing part17. The clutch mechanism permits rotational movement of the drive member20 with respect to the stop member 26, when the rotation member rotatesin the second direction with respect to the housing part 17.

Thus, the rotation member 21 may rotate with respect to the drive member20 and the stop member 26 in the first direction during setting of thedose, with rotation of the drive member being prevented by itsinteraction with the stop member, and rotation member as well as drivemember may rotate with respect to the stop member in the seconddirection during delivery of the dose.

The stop member may be arranged to abut and/or engage the drive memberduring setting of the dose and, preferably, during delivery of the dose.The stop member 26 has a toothing 27 at one end which faces the drivemember, e.g. its proximal end. The teeth may be ramp-shaped with a steepside and a less steep ramp. The teeth may be disposed azimuthally alongthe perimeter of the stop member.

Drive member 20 has a toothing 28 at one end which faces the stopmember, e.g. its distal end. Toothings 22 and 28 of the drive member 20are oppositely disposed. Toothing 28 may be configured in accordancewith toothing 21 of the rotation member. Toothing 22 may be configuredin accordance with toothing 27 of the stop member. Toothings 27 and 28,in particular the steep sides of the teeth, do cooperate, e.g. abut, forpreventing rotation of the drive member 20 with respect to the housingpart 17 and, in particular, with respect to the stop member 26 in thefirst direction.

Stop member 26 is preferably secured against rotational movement withrespect to the housing part 17. Stop member 26 may be fixed to thehousing or integrated into the housing. Stop member 26 may be fixedagainst displacement with respect to the housing part 17 or displacementwith respect to the housing part 17 may be allowed.

As it is illustrated in the present embodiment, stop member 26 isdisplaceable with respect to the housing but non-rotatable with respectto the housing part 17. For that purpose, one or a plurality of,preferably oppositely disposed, guide features, for example guide lugs29, are provided in the stop member 26. The respective guide feature 29engages a corresponding guide slot 30 which may be provided in thehousing, e.g. in housing part 17. This can be seen in FIGS. 2 to 5. Aguide feature 29 cooperates with a guide slot 30 to prevent rotationalmovement of the stop member with respect to the housing part 17, withaxial movement of the stop member 26 with respect to the housing beingallowed. The axial movement of the stop member 26 may compensate forplay between components of the drive mechanism during operation.

From the group comprising drive member 20, stop member 26 and rotationmember 21 one or more members, preferably two members or three members,may be axially displaceable with respect to the housing part 17 and,preferably, with respect to the piston rod 12. Therein, the drive memberand another one of the recited members may be axially displaceable withrespect to the housing. The remaining member may be secured againstaxial displacement or may also be axially displaceable during operationof the drive mechanism for medication delivery. Accordingly, if thedrive member and the stop member are axially displaceable, the rotationmember may be axially secured or axially displaceable and so on. Playbetween the components caused by relative (axial) movement of componentsof the clutch mechanism with respect to the housing can be compensatedfor in this way. The distance by which the respective components may beaxially displaced with respect to the housing may correspond to the(maximum) depth of a tooth of the respective toothing 22 or 28 of thedrive member. Alternatively, the distance may be greter than the(maximum) depth of a tooth of the respective toothing.

Furthermore, the drive mechanism comprises a resilient member 31,preferably a spring member. The resilient member 31 may be biased duringmedication delivery operation of the drive mechanism. The resilientmember may provide for a force that tends to keep the drive member 20 inengagement with the stop member 26 and/or the rotation member 21. Theforce may be exerted along the rotation axis. In the situation shown inFIGS. 2 to 5, this force may be exerted in the proximal direction. Theresilient member 31 may be a helical (coil) spring. The resilient member31 may be a compression spring.

The resilient member 31 may keep the drive member 20 and the stop member26 in (permanent) mechanical contact, e.g. in abutment, with each otherduring setting and delivery of a dose of the medication. Alternativelyor additionally, the resilient member 31 may keep the drive member 20and the rotation member 26 in (permanent) mechanical contact, preferablyabutment, with each other during setting and delivery of a dose of themedication.

The resilient member 31 may be integrated within stop member 26 or aseparate component. The resilient member 31 may be arranged on thedistal end side of the stop member 26.

The drive mechanism furthermore comprises a support member 32. Supportmember 32 is expediently fixed against axial and rotational movementwith respect to the housing part 17 or integrated into housing part 17.Support member 32 is arranged on that side of the drive member 20 whichis remote from the stop member 26. Support member 32 may be aprotrusion, for example a ring-like protrusion. Rotation member 21 mayextend through an opening in support member 32. The support member 32may provide for a counter force to the force which is exerted by theresilient member 31. Permanent abutment of the rotation member with thedrive member and of the drive member with the stop member during settingand delivery of medication is facilitated in this way.

The rotation member 21 has an (radially) outwardly protruding member 33,for example a flange portion. The protruding member 33 is expedientlyprovided for abutting support member 32, in particular the distal endside of support member 32.

Another support 48 (cf. FIG. 6) may be provided for providing acounterforce to the force exerted by the resilient member 31. Support 48is arranged on that side of the drive member 20 which is remote from therotation member 21. Support 48 is arranged on that side of the stopmember 26 which is remote from the support member 32. The support 48 maybe arranged to abut the resilient member 31. The support 48 may besecured against axial and rotational movement with respect to thehousing part 17, with respect to the housing 13 or integrated into thehousing 13, for example into (additional) housing part 40 (cf. FIG. 6).

The drive mechanism furthermore comprises a dose member 34. Dose member34 may be dose part 16 or may be a part of the dose part 16 of FIG. 1.Dose member 34 is movable with respect to the housing in the proximaldirection for setting of a dose and for delivery of the dose. Forexample, the dose member 34 may be moved in the proximal direction withrespect to the housing part 17 during dose setting and in the distaldirection with respect to the housing part 17 during dose delivery. Thedose member 34 may engage the housing part 17 or, alternatively, anotherpart of housing 13 (not explicitly shown). Dose member 34 is preferablysecured against rotational movement with respect to the housing part 17.The dose member 34 may comprise a guide feature 35, for example a guidelug or a guide slot, that engages another guide feature, for example aguide slot or a guide lug, respectively, that is provided in the housingpart 17 or the housing 13.

Dose member 34 may be moved in the proximal direction and in the distaldirection with respect to rotation member 21. Dose member 34 is arrangedto be couplable and is preferably (permanently) coupled to rotationmember 21 such that movement of the dose member, e.g. in the proximaldirection with respect to the housing part 17, for setting a dose of themedication is converted into rotational movement of the rotation memberin the first direction and movement of the dose member, e.g. in theproximal direction with respect to the housing part 17, for deliveringthe dose is converted into rotational movement of the rotation member 21in the second direction opposite to the first direction.

The rotation member 21 may be provided with an (outer) thread 36. Thread36 may be engaged with one of or a plurality of engagement members 42 ofdose member 34. The respective engagement member may be arranged on theinside of the dose member. The respective engagement member may be athread or a part of a thread, for example. Thus, dose member 34 androtation member 21 may be threadedly coupled, in particularly threadedlyengaged. The rotation member 21 may be arranged inside the dose member21.

The rotation member 21, the drive member 20, the stop member 26 and/orthe dose member 34 may be or may comprise a respective sleeve. Thepiston rod 12 may be arranged to be driven and, in particular, may bedriven through one of, more of or all of those sleeves. The piston rod12 may run through one of, more of or all of those sleeves.

The drive member 20 and the piston rod 12 are configured for rotationalmovement of the drive member 20 with respect to the housing beingconverted into rotational movement of the piston rod with respect to thehousing. The drive member 20 may engage the piston rod 12. The pistonrod 12 is displaceable with respect to the drive member 20 along adisplacement axis. Presently, the displacement axis runs along therotation axis. The drive member 20 may be splined to the piston rod 12,for example.

The piston rod 12 is threadedly coupled to the housing 13. The pistonrod 12 may be provided with an outer thread 49, for example. The pistonrod 12 may extend through and be engaged with a (part) thread in opening39 which is provided in housing part 40, for example in support 48 (cf.FIG. 6). Housing part 40 may be formed integrally with housing part 17,may be a housing part fixed thereto or may be a housing part securedseparately from housing part 17 to housing 13.

The piston rod 12 comprises an engagement track 37, preferably twooppositely disposed engagement tracks, on the outside. The (respective)engagement track 37 may interrupt thread 49. The (respective) engagementtrack 37 preferably extends along the axia along which the piston rod isdisplaceable with respect to the housing and, in particular, withrespect to the drive member.

Rotational movement of the drive member 20 with respect to the housingmay thus be converted into rotational movement of the piston rod 12 withrespect to the housing and the rotational movement of the piston rod 12is, on account of the threaded engagement of the piston rod and thehousing (part), converted into movement of the piston rod with respectto the housing in the distal direction.

The dose part 16 (cf. FIG. 1) may comprise a dose knob 41 (cf. FIG. 8).Dose knob 41 may be configured to be gripped by a user. Dose knob 41 maybe arranged and connected to the dose member 34 at the proximal end.Dose knob and dose member may be unitary.

In the following, operation of the present drive mechanism fordelivering medication from the cartridge 4 of FIG. 1 is described.

To set a dose, a user may manually move dose member 34 in the proximaldirection (arrow 43) with respect to the housing part 17 (cf. FIGS. 2,3, 8 and 9). To do so, the user may grip dose knob 41 and pull it in theproximal direction. Dose member 34 moves proximally also with respect tothe rotation member 21. Proximal movement of the rotation member isprevented by support member 32 which abuts protruding member 33 ofrotation member 21. Consequently, the proximal movement of dose member34 with respect to the housing part 17 is converted into rotationalmovement of the rotation member 21 in the first direction (arrow 44)with respect to the housing part 17, in particular on account of thethreaded engagement of dose member 34 and rotation member 21. Thus, therotation member 21 rotates in the first direction—counter-clockwise asseen from the proximal end of the rotation member—with respect to thehousing. Rotation member 21 also rotates with respect to the drivemember 20 and to the stop member 26. The drive member 20 is preventedfrom rotating in the first direction by interaction with the stop member26, e.g. by interlocking of toothings 27 and 28. As the piston rod 12 iscoupled to the drive member 20 and rotation in the first direction ofthe drive member would cause the piston rod to travel in the proximaldirection, the piston rod 12 is prevented from being driven in theproximal direction by interaction of stop member 26 and drive member 20.Dose accuracy can be increased in this way.

When the rotation member 21 rotates in the first direction, the ramps ofthe teeth of toothing 23 of rotation member 21 slide along the ramps ofthe teeth of toothing 22. Thus, a tooth of the rotation member may indexaround the rotation axis until the tooth engages one of the next teethof toothing 22 of drive member 20. The teeth of rotation member 21 slidealong the ramps of the teeth of drive member 20. During this movement,drive member 20 and, in particular, stop member 26 are displaced alongthe rotation axis with respect to piston rod 12 and housing by adistance determined by, preferably equal to, the depth of a tooth oftoothing 22, before a tooth of toothing 23 (totally) disengages thattooth of toothing 22. Afterwards, the tooth of the rotation member 21engages the next tooth of toothing 22 and the force provided byresilient member 31 moves drive member 20 and, in particular, stopmember 26 back along the rotation axis into the axial start position. Anaccording movement of stop member and drive member in the distaldirection and back into the proximal direction is indicated by doublearrow 45 in FIGS. 2 and 3.

A tooth of the rotation member which engages the next tooth of the drivemember may cause an audible and/or tactile feedback to the user.

The drive mechanism is suitabe for a fixed dose device or a usersettable dose device. The size of the fixed dose of medication which isto delivered or the increments in which a user-settable dose may bevaried by a user are preferably determined by the distribution of theteeth of the respective toothings in the drive member, rotation memberand stop member. The rotation member may be rotated over more than oneteeth (dose increment) of the drive member for a user-settable dosedevice and over one teeth (only) for a fixed dose device. The number ofteeth in the drive member 20 over which the rotation member 21 rotatesduring dose setting determines the size of the dose which is actuallydelivered. The dose member and the rotation member may be adapted to oneanother such that the rotation member may rotate only by one tooth for afixed dose device and by more than one tooth for a variable dose device.

After the dose has been set, the dose part 16 and with it the dosemember 34 is moved (pushed) by the user in the distal direction withrespect to housing part 17 (arrow 46; cf. FIGS. 4, 5, 8 and 9). Thus,the dose member 34 is moved in the distal direction with respect to thehousing part 17. The rotation member 21 accordingly rotates in thesecond direction, which is opposite to the first direction, with respectto the housing (arrow 47, cf. FIGS. 4 to 9). Drive member 20 followsrotational movement of the rotation member in the second direction.Rotational movement of the drive member 20 in the second direction isconverted into rotational movement of the piston rod 12 in the seconddirection, which movement, in turn, is converted into movement of thepiston rod 12 in the distal direction. Accordingly, the piston 10 ofFIG. 1 may be displaced in the distal direction with respect to thecartridge 4 and a dose of medication 5 is dispensed from the cartridgethe amount of which corresponds to the previously set dose.

During dose delivery, toothings 22 and 23 interlock and ramps of theteeth of toothing 28 of the drive member 20 slide along ramps of theteeth of toothing 27 of stop member 26. This movement is similarly asdescribed above for the relative rotational movement of rotation memberand drive member with opposite rotation direction. The stop member 26 isthereby displaced in the distal direction with respect to the drivemember 20 by a distance corresponding to the depth of a tooth oftoothing 27 in stop member 26. Resilient member 28 forces the stopmember 26 back into the axial starting position, when the next tooth oftoothing 28 is engaged by the respective tooth of toothing 27 (doublearrow 65).

A tooth of the drive member which engages the next tooth of the stopmember may cause an audible and/or tactile feedback to the user.

FIG. 10 schematically shows an oblique sectional view of a secondembodiment of a drive mechanism. This drive mechanism essentiallycorresponds to the one described in conjunction with FIGS. 2 to 9. Incontrast thereto, the stop member 26 is secured against rotationalmovement and displacement with respect to the housing (13, 17, 40). Stopmember 26 may be integrated in housing part 40 or 17 or an insertthereof. Housing part 40 may be housing 13, for example. Housing part 17may be inserted and fixed within housing 13. Fixing elements 64 mayengage corresponding elements in the housing for fixing the housing part17 to housing part 40.

In order to compensate for the relative axial displacement betweenrotation member 21, drive member 20 and stop member 26, when therespective parts rotate with respect to one another, the rotation member21 is movable with respect to the housing. In order to keep stop member26 and rotation member 21 in, preferably permanent, abutment with drivemember 20 during medication delivery operation of the drive mechanism,resilient member 31 exerts a force on the rotation member 21, preferablyon protruding member 33 thereof which presses rotation member and drivemember 20 towards stop member 26. Resilient member 31 may be arranged atthat side of the drive member which faces away from the stop member,e.g. its proximal side. Resilient member may abut the proximal face ofprotruding member 33. Support member 32 can thus be dispensed with. Thedistal end face of housing part 17 may act as an abutment surface forthe resilient member 31.

However, when the elements are arranged as shown in FIG. 10, axialmovement of the rotation member, which may occur correspondingly to theaxial movement of the stop member in the previous embodiment, may betransferred to the dose part 16 and thereby to the user. This movementof an external part might be irritating for a user.

FIGS. 11 to 15 schematically show a third embodiment of a drivemechanism which is suitable for being provided in the medicationdelivery device 1 as described in conjunction with FIG. 1.

The drive mechanism essentially corresponds to the one described inconnection with the previous embodiments. In contrast thereto, the drivemember 20 and, in particular, the rotation member 21 are rotatablearound a rotation axis which runs obliquely with respect to the axisalong which the piston rod 12 is displaced (displacement axis). Therotation axis (cf. axis A in FIG. 14) may run transversally, inparticular perpendicularly, with respect to the displacement axis and,in particular, with respect to a main direction of extent of the pistonrod 12.

Drive member 20 and rotation member 21 may be retained by an axis member50, which may extend through rotation member 21 and drive member 20.Axis A may run along axis member 50. Axis member may secure drive memberand rotation member against displacement with respect to the housing.Stop member 26 may be integrated into housing 13. Of course, stop member26 may also be embodied as a separate element. Axis member 50 may extendthrough stop member 26.

Drive member 20 comprises an outer toothing 51. Teeth of the outertoothing 51 may extend radially away from rotation axis A. Drive membermay be a toothed gear sleeve. The piston rod 12 is expediently providedwith an outer toothing 52. The outer toothing 52 of piston rod 12 andthe outer toothing 51 of the drive member 20 are arranged to engage oneanother. The outer toothing 52 of piston rod 12 and the outer toothing51 of the drive member 20 may be permanently engaged. When the drivemember 20 and the rotation member 21 rotate together in the seconddirection with respect to the housing 13, the piston rod 12 is alsodisplaced in the distal direction with respect to the housing. Thepiston rod does not rotate while it is displaced in the distal directionwith respect to the housing.

The piston rod 12 may be supported against deviation in the radialdirection with respect to the displacement axis, for example by means ofhousing part 17 through an opening 53 in which the piston rod mayextend.

In contrast to the previously described embodiments, the dose member 34and the rotation member 21 are not threadedly engaged. Rather, rotationmember 21 and dose member 34 are connected/coupled to one another via alever mechanism. The lever mechanism is adapted to convert movement ofthe dose member 34 with respect to the housing in the proximal directioninto rotational movement of the rotation member in the first directionwith respect to the housing and movement of the dose member 34 withrespect to the housing in the distal direction into rotational movementof the rotation member in the second direction with respect to thehousing.

Drive member 20 is prevented to rotate during setting of the dose onaccount of the stop member 26 preventing rotational movement of thedrive member in the first direction.

The lever mechanism may comprise a lever 55. Lever 55 is preferablysecured against rotational movement with respect to rotation member 21and preferably against (simultaneous) translational movement withrespect to rotation member 21. Preferably, lever 55 is formed unitarywith rotation member 21. Lever 55 is pivotally around the rotation axisin the first direction during dose setting and in the second directionduring dose delivery.

Dose member 34 may, preferably at its distal end, comprise an engagementmember 54, e.g. a pin, for engagement with the lever 55. Engagementmember 54 may engage the lever 55, in particular an opening 56,preferably an elongate opening 56 within lever 55.

Stop member 26 prevents rotational movement of the drive member in thefirst direction during dose setting as described previously.

FIG. 16 shows a schematic sectional view of a part of a resettable drivemechanism according to an embodiment in a delivery state. FIG. 17 showsthe resettable drive mechanism of FIG. 16 in a reset state.

The drive mechanism may correspond to the one described in conjunctionwith FIGS. 2 to 9. However, a reset mechanism for a drive mechanism asit is described in more detail below may also be provided for in theremaining drive mechanisms as described above.

The drive mechanism described in conjunction with FIGS. 15 and 16 is aresettable drive mechanism. For this purpose, the drive mechanismcomprises a reset mechanism. The reset mechanism may be switched betweena reset position and a delivery position.

In contrast to the drive mechanism described in conjunction with theprevious figures, the rotation member 21 is not shown in FIGS. 16 and17. However, a rotation member may nevertheless be provided. FIGS. 16and 17 only show a half of a section through the drive mechanism. Theadditional cut was made along piston rod 12.

As shown in FIG. 16, in the delivery state, drive member 20 and stopmember 26 are engaged with one another such that rotational movement ofthe drive member 20 with respect to housing 13 in the first direction isprevented and rotation of the drive member 20 in the second direction,opposite to the first direction, is allowed. Toothings 27 and 28 may beprovided for this purpose as described further above.

Resilient member 31 exerts a force acting in axial direction on stopmember 26, said force tending to keep the stop member and the drivemember engaged. Resilient member 31 may be arranged to keep stop memberin engagement and, in particular, in abutment with drive member 20 inthe delivery state. The (biased) resilient member 31 may be supported byand, preferably, bear against bearing member 57. Bearing member may besupport 48 of FIG. 6, for example. Bearing member 57 is expedientlysecured against rotational movement and displacement with respect tohousing 13.

Rotation of the drive member 20 in the second direction may cause thepiston rod 12 to be displaced in the distal direction with respect tohousing 13. The piston rod 13 may rotate and translate in the distaldirection with respect to the housing for dose delivery as described inconjunction with FIGS. 2 to 10. Alternatively, the piston rod may bemoved in the distal direction with pure translatory movement (notexplicitly shown, cf. a drive mechanism according to FIGS. 11 to 15).The drive member 20 may engage the piston rod 12. The drive member 20may be splined to the piston rod 12. Preferably, there is no relativerotational movement possible between piston rod 12 and drive member 20.Also, the drive member 20 preferably cannot be rotated in the firstdirection on account of the (permanent) interlocking of the drive member20 and the stop member 26 when the reset mechanism is in the deliverystate.

Thus, when the drive mechanism is in the delivery state, movement of thepiston rod 12 in the proximal direction with respect to housing 13 to astarting position is prevented, because the stop member 26 preventsrotation of the drive member 20 in the first direction and the drivemember has to be rotated in the first direction, if the piston rod 12was to be moved in the proximal direction with respect to the housing 13into the starting position.

However, after a cartridge 4 has been emptied, i.e. after a distal endposition of the piston 10 and, in particular, of the piston rod 12 hasbeen reached, the piston rod has to be moved in the proximal directionback into a proximal starting position in order to allow the drivemechanism to be reused. Expediently, the drive mechanism is configuredto be switchable from the delivery state to a reset state. In the resetstate, the piston rod 12 may be moved in the proximal direction withrespect to the housing, for example by a user screwing and/or pushingthe piston rod 12 in the proximal direction.

The drive mechanism comprises a clutch member 58. Clutch member 58 ismovable with respect to housing 13, preferably displaceable with respectto the housing, between a delivery position D and a reset position R.The clutch member 58 may be moved back and forth between the deliveryposition and the reset position. The reset position may be arranged inthe distal direction as seen from the delivery position. The clutchmember 58 may be a sleeve. Piston rod 12 may extend through clutchmember.

In the delivery position, drive member 20 and stop member 26 areengaged. In the reset position, drive member 20 and stop member 26 aredisengaged (cf. the encircled region 59 in FIG. 17). Thus, when theclutch member 58 is in the reset position, the drive member may berotated in the first direction with respect to the housing 13 withoutthe stop member 26 preventing the rotation. Consequently, the piston rod12 may be moved in the proximal direction, e.g. by rotation with respectto the housing and on account of a threaded engagement to the housing,due to the drive member 20 and the stop member 26 being disengaged.

The clutch member 58 may comprise a protrusion 61. Protrusion 61 mayprotrude radially and preferably inwardly from a base portion 66 of theclutch member 58. The base portion may extend in the axial direction.Protrusion 61 may be arranged to move the drive member 20 and the stopmember 26 out of engagement when the clutch member is moved towardsreset position R. Protrusion 61 may be provided at or near the proximalend of the clutch member 58. A distal end face of protrusion 61 ofclutch member 58 may be arranged to couple to and preferably to abut aproximal face of stop member 26.

The reset mechanism furthermore comprises a clutch resilient member 60,for example a clutch spring member, like a coil spring and/or acompression spring, for example.

The clutch member 58 may extend along drive member 20, stop member 26,resilient member 31, bearing member 57 and/or clutch resilient member60. The clutch member 58 may be rigid. The clutch member 58 may have aconstant length.

Clutch resilient member 60 may be biased when the clutch member 58 is inthe delivery position. Biased clutch resilient member may exert a forceon the clutch member that tends to move the clutch member in the resetposition. Clutch resilient member 60 may bear on bearing member 57, inparticular on a distal face thereof.

Clutch member 58 may comprise a (additional) protrusion 62. Protrusion62 may protrude radially and preferably inwardly from the base portion66 of the clutch member 58. Protrusion 62 may be arranged in the regionof the distal end of the clutch member 58. Protrusion 62 may be arrangedto be abuttable by and is preferably abutted by clutch resilient member60. Clutch resilient member 60 may be supported by and, in particular,bear on a proximal face of protrusion 62.

The clutch resilient member 60 is arranged to exert a force on theclutch member 58 which force tends to move the clutch member 58 in thereset position R. When the drive mechanism is in the delivery state,this force is counteracted by a clutch stop member 63. Accordingly, inthe delivery state, clutch member 58 may be held in the deliveryposition by the clutch stop member 63.

In the delivery state, clutch stop member 63 is preferably securedagainst displacement with respect to the housing 13. Clutch stop member63 may be arranged to abut clutch member 58. A proximal end face of theclutch stop member 63 may abut a distal end face of the clutch member 58in the delivery state.

For resetting the device, the clutch stop member 63 may be moved, forexample removed, so as to allow the clutch member to move into the resetposition. Thereupon, biased clutch resilient member 60 which exerts theforce, which is no longer compensated by clutch stop member, on clutchmember 58. The force automatically tends to move clutch member 58 in thereset position R. The clutch member 58 may abut stop member 26. Stopmember 26 may tend to follow movement of the clutch member towards thereset position R.

In order to get into reset position the force exerted by the resilientmember 31 on the stop member 26, which force tends to hold drive member20 and stop member 26 in engagement, has to be overcome. Thus, the forcemoving the clutch member 58 towards the reset position 58 has to begreater than the force exerted by the resilient member 31. The force formoving and, in particular, holding the clutch member 58 in resetposition R may be provided for by clutch resilient member 60. It isexpedient for the resilient member 31 and the clutch resilient member 60to be embodied as a spring member, respectively. Clutch resilient member60, in this case, preferably has a spring strength greater than the oneof resilient member 31 in order to overcome the force exerted byresilient member 31.

The clutch stop member 63 is expediently formed in the cartridge unit,for example, by the cartridge 4 or the cartridge retaining member 11.Thus, if the cartridge unit is detached from the housing 13 forreplacing an empty cartridge, the clutch member 58 is moved, preferablyautomatically, towards and into the reset position and preferably heldin the reset position.

The distance by which the clutch member 58 moves with respect to thehousing 13 when moving from delivery position into reset position ispreferably chosen to be great enough to disengage toothings 27 and 28.

The clutch member 58 is expediently secured to the drive mechanism inorder to avoid the clutch member falling out of the housing. For thispurpose, the clutch member may abut a proximal face of the stop member26.

As shown in FIG. 17, when the clutch member 58 is in reset position R,the drive mechanism is in the reset state and the piston rod 12 may bemoved in the proximal direction with respect to the housing from adistal end position back into a proximal starting position. When a newcartridge 4 is attached to the housing 13, after the piston rod 12 wasmoved back into starting position, clutch member 58 may be moved intothe distal direction back into delivery position together with thecartridge 4 and, if present, the cartridge retaining member 11, therebymoving drive member 20 and stop member 26 again into engagement.

Accordingly, the medication delivery device may be reused. As an elementof the cartridge unit like cartridge 4 or cartridge retaining member 11may serve as the clutch stop member 63, the reset mechanism mayautomatically and, in particular (purely) mechanically, decouple stopmember 26 and drive member 20, when the cartridge unit 2 is detachedfrom the drive unit 3 (cf. FIG. 1). Thus, the only action required by auser is to move, e.g. screw and/or push, the piston rod 12 back into thestarting position before a new cartridge unit 2 may be attached to thedrive unit 3. The drive mechanism is thus easily reusable.

The reset mechanism described herein above may be implemented easily andrequires only a small amount of additional parts such as compared to thecorresponding non-resettable drive mechanism. In particular, such ascompared to the first embodiment, only two additional parts—clutchmember and clutch resilient member—are required for the automatic resetmechanism.

As the reset mechanism may be an automatic one, no external action isrequired for disengaging stop member and drive member. Thus, the clutchmember may be retained in the housing and, in particular, inaccessiblefrom the outside.

Of course, the reset mechanism may be implemented as a manual,non-automatic mechanism. It is expedient, in this case, to configure themovement of the clutch member to be externally actuable.

In contrast to the situation depicted in FIGS. 16 and 17, the clutchmember 58 may be (partly) arranged outside of the housing. The housingmay be provided with one or more openings through which the clutchmember may extend from the outside to the inside of the housing. This isparticularly expedient for a non-automatic reset mechanism.

With the (resettable) drive mechanisms described herein above a gooddose accuracy may be achieved. The drive mechanisms are particularlysuitable for dispensing doses of the medication from and including 1 IUup to and including 30 IU, preferably from and including 3 IU up to andincluding 20 IU. Also, doses of 30 IU or more or 1 IU or less may bedispensed by means of the described drive mechanisms. However, doses offrom and including 1 IU up to and including 30 IU are particularlysuitable. For example, if a device described in conjunction with FIGS. 1to 10, in which the piston rod rotates during displacement, was to bedesigned for doses less than 1 IU, the thread of the piston rod shouldhave a low pitch and/or the number of teeth of the respective toothingof drive member and rotation member should be increased. Of course, theproduction costs may increase on account of the finer segmentation ofthe toothings and the lower pitch thread. In order to provide for adevice configured to deliver doses greater than 30 IU, e.g. 50 IU orgreater, the thread in the piston rod should have a higher pitch.Consequently, small deviations from a predetermined course of the threadresult in major absolute deviations from the desired dose. Thus, therisk of a reduction in dose accuracy may be increased. In addition, therisk of self-locking of a threaded engagement may be increased.

A diameter of the (outer) housing of the medication delivery device maybe less than or equal to 20 mm, preferably less than or equal to 16 mm,particularly preferably less than or equal to 14 mm.

A first aspect of the invention provides a resettable drive mechanismfor a medication delivery device (1), comprising:

a housing (13, 17, 40) with a proximal end and a distal end,

a drive member (20) rotatable with respect to the housing in a seconddirection for delivering a dose of a medication,

a piston rod (12) adapted to be driven in a distal direction withrespect to the housing by the drive member, when the drive memberrotates in the second direction,

a stop member (26) adapted to prevent rotation of the drive member in afirst direction opposite to the second direction with respect to thehousing, when the stop member engages the drive member, and

a clutch member (58) movable with respect to the housing between adelivery position (D) and a reset position (R), wherein,

when the clutch member is in the delivery position, the stop member andthe drive member are engaged and the drive member is prevented fromrotating in the first direction with respect to the housing, and

when the clutch member is in the reset position, the drive member andthe stop member are disengaged, the drive member is rotatable in thefirst direction with respect to the housing and the piston rod ismovable in the proximal direction with respect to the housing.

A second aspect provides a drive mechanism according to the firstaspect, wherein the drive member (20) engages the piston rod (12).

A third aspect provides a drive mechanism according to the first orsecond aspect, wherein the drive mechanism comprises a clutch resilientmember (60) which is arranged to exert a force on the clutch member (58)which force tends to move the clutch member in the reset position (R)when the clutch member is moved towards the delivery position (D) or isin the delivery position.

A fourth aspect provides a drive mechanism according to the thirdaspect, wherein the drive mechanism comprises a removable clutch stopmember (63) that is arranged to counteract the force, thereby preventingthe clutch member (58) from moving in the reset position (R).

A fifth aspect provides a drive mechanism according to any one of thefirst through fourth aspects, wherein the drive mechanism comprises aresilient member (31) which exerts a force on one of or both of thedrive member (20) and the stop member (26) which force tends to keep thedrive member and the stop member in engagement.

A sixth aspect provides a drive mechanism according to the third andfourth aspects, wherein the clutch resilient member (60) is a clutchspring member and the resilient member (31) is a spring member, theclutch spring member having a spring strength which is greater than aspring strength of the spring member.

A seventh aspect provides a drive mechanism according to any one of thefirst through sixth aspects, wherein the drive member (20) and the stopmember (26) are engaged to form a unidirectional friction clutchmechanism when the clutch member is in the delivery position (D).

An eighth aspect provides a drive mechanism according to any one of thefirst through seventh aspects, wherein the stop member (26) is securedagainst rotational movement with respect to the housing (13, 17, 40) andthe stop member is displaceable with respect to the housing.

A ninth aspect provides a drive mechanism according to any one of thefirst through eighth aspects, wherein the stop member (26) is arrangedto follow movement of the clutch member (58) towards the reset position(R), thereby disengaging from the drive member (20).

A tenth aspect provides a drive mechanism according to any one of thefirst through ninth aspects, wherein the clutch member (58) is arrangedto abut the stop member (26) when the clutch member is moved towards thereset position (R).

An eleventh aspect provides a medication delivery device (1) comprisinga resettable drive mechanism according to any one of the first throughtenth aspects, and a cartridge (4) for holding a medication (5), thecartridge being releasably attached to the housing (13, 17, 40).

A twelfth aspect provides a medical delivery device according to theeleventh aspect, with a drive mechanism according to the fourth aspect,wherein the cartridge (4) or a cartridge retaining member (11) is theclutch stop member (63).

Of course, the invention is not restricted by the embodiments describedabove.

LIST OF REFERENCE NUMERALS

1 medication delivery device

2 cartridge unit

3 drive unit

4 cartridge

5 medication

6 outlet

7 distal end of the device

8 proximal end of the device

9 membrane

10 piston

11 cartridge retaining member

12 piston rod

13 housing

14 proximal end side of the cartridge unit

15 distal end side of the housing

16 dose part

17 housing part

18 proximal end of housing part

19 distal end of housing part

20 drive member

21 rotation member

22 toothing

23 toothing

24 tooth

25 tooth

26 stop member

27 toothing

28 toothing

29 guide feature

30 guide slot

31 resilient member

32 support member

33 protruding member

34 dose member

35 guide feature

36 thread

37 engagement track

38 engagement feature

39 opening

40 housing part

41 dose knob

42 engagement member

43, 44, 45, 46, 47 arrow

48 support

49 thread

50 axis member

51 outer toothing of drive member

52 toothing of piston rod

53 opening

54 engagement means

55 lever

56 opening

57 bearing member

58 clutch member

59 encircled region

60 clutch resilient member

61 protrusion

62 protrusion

63 clutch stop member

64 fixing element

65 arrow

66 base portion

A axis

1. A resettable drive mechanism for a medication delivery device (1),comprising: a housing (13, 17, 40) with a proximal end and a distal end,a drive member (20) rotatable with respect to the housing in a seconddirection for delivering a dose of a medication, a piston rod (12)adapted to be driven in a distal direction with respect to the housingby the drive member, when the drive member rotates in the seconddirection, a stop member (26) adapted to prevent rotation of the drivemember in a first direction opposite to the second direction withrespect to the housing, when the stop member engages the drive member,and a clutch member (58) movable with respect to the housing between adelivery position (D) and a reset position (R), wherein, when the clutchmember is in the delivery position, the stop member and the drive memberare engaged and the drive member is prevented from rotating in the firstdirection with respect to the housing, and when the clutch member is inthe reset position, the drive member and the stop member are disengaged,the drive member is rotatable in the first direction with respect to thehousing and the piston rod is movable in the proximal direction withrespect to the housing.
 2. The drive mechanism of claim 1, wherein thedrive member (20) engages the piston rod (12).
 3. The drive mechanism ofclaim 1, wherein the drive mechanism comprises a clutch resilient member(60) which is arranged to exert a force on the clutch member (58) whichforce tends to move the clutch member in the reset position (R) when theclutch member is moved towards the delivery position (D) or is in thedelivery position.
 4. The drive mechanism of claim 3, wherein the drivemechanism comprises a removable clutch stop member (63) that is arrangedto counteract the force, thereby preventing the clutch member (58) frommoving in the reset position (R).
 5. The drive mechanism of claim 1,wherein the drive mechanism comprises a resilient member (31) whichexerts a force on one of or both of the drive member (20) and the stopmember (26) which force tends to keep the drive member and the stopmember in engagement.
 6. The drive mechanism of claim 3, wherein thedrive mechanism comprises a resilient member (31) which exerts a forceon one of or both of the drive member (20) and the stop member (26)which force tends to keep the drive member and the stop member inengagement.
 7. The drive mechanism of claim 6, wherein the clutchresilient member (60) is a clutch spring member and the resilient member(31) is a spring member, the clutch spring member having a springstrength which is greater than a spring strength of the spring member.8. The drive mechanism of claim 1, wherein the drive member (20) and thestop member (26) are engaged to form a uni-directional friction clutchmechanism when the clutch member is in the delivery position (D).
 9. Thedrive mechanism of claim 1, wherein the stop member (26) is securedagainst rotational movement with respect to the housing (13, 17, 40) andthe stop member is displaceable with respect to the housing.
 10. Thedrive mechanism of claim 1, wherein the stop member (26) is arranged tofollow movement of the clutch member (58) towards the reset position(R), thereby disengaging from the drive member (20).
 11. The drivemechanism of claim 1, wherein the clutch member (58) is arranged to abutthe stop member (26) when the clutch member is moved towards the resetposition (R).
 12. A medication delivery device (1) comprising aresettable drive mechanism according to claim 1, and a cartridge (4) forholding a medication (5), the cartridge being releasably attached to thehousing (13, 17, 40).
 13. The device of claim 12 comprising a drivemechanism according to claim 4, wherein the cartridge (4) or a cartridgeretaining member (11) is the clutch stop member (63).